OBJ Files
A 3D Object Format

These are some examples of OBJ files. An OBJ file is good for storing a description of the surface of a 3D object, composed of triangles or higher degree polygons.

OBJ File Characteristics:

• ASCII (there is also a binary version, for which an "MOD" extension is used in the file name);
• Color;
• 3D;
• No compression;
• contain definitions of 1 or more named 3D objects;

Related Data and Programs:

An OBJ file may define and access an external MTL file, which contains definitions of various material types.

Reference:

1. http://www.alias.com/eng/index.shtml, The Alias web site.
2. ../../txt/obj_format.txt, some information about the OBJ format.

Routines to read an OBJ file:

• OBJ_IO includes routines that will read 3D graphics data from an OBJ file;

Routines to write an OBJ file:

• OBJ_IO includes routines that will write 3D graphics data as an OBJ file;
• The routine voxel_to_obj in the MRI library region.

Programs to convert an OBJ file to another format:

• ivcon can read in an OBJ file, and write it out in a variety of formats;
• ivread can read in an OBJ file, and write it out in a variety of formats;
• obj2opengl is a PERL script that converts an OBJ file to a C/C++ include file appropriate for use with Open GL;
• obj_2_ply is a C program that reads an OBJ file and writes a PLY file.

Programs to convert a file to OBJ format:

• IVCON can read in a variety of 3D file formats, and write them out as OBJ files;
• IVREAD can read in a variety of 3D file formats, and write them out as OBJ files;
• PLY_TO_OBJ is a C program which reads a PLY 3D graphics file and writes an equivalent OBJ graphics file.
• TEC_TO_OBJ is a FORTRAN90 program which can read a TECPLOT file describing a surface in 3D composed of triangles or quadrilaterals, and write an OBJ file.
• The Visual Toolkit routine vtkOBJExporter can export a VTK image to an OBJ file.

Sample OBJ files:

• cessna.obj, a Cessna airplane;
• cube.obj, a cube;
• gourd.obj, a gourd;
• humanoid_quad.obj, a humanoid shape of 48 quadrilateral faces;
• humanoid_tri.obj, a humanoid shape of 96 triangular faces;
• humanoid_tri.png, a PNG image of the humanoid shape;
• magnolia.obj, a magnolia blossom;
• shuttle.obj, the Space Shuttle;
• tetrahedron.obj, a tetrahedron;

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